O.D.'s Measure Small, I.D.'s Measure Large ?

Does anyone know why when using a Romer PCMM, the measurements for outer diameters measure small, while the inner diameters measure large?

I was told from Romer tech support that it is the deflection of the probe. I find it hard to believe that the probe is deflecting .010 when using the 6mm probe and a soft touch.

I'm getting the same results with both or our Romer arms, and with either the 3mm or 6mm probes. I also get the same results when using our PowerInspect software. Both arms have been calibrated recently.

Any thoughts or is anyone else experiencing the same issue?

cmmguy over 17 years ago

Do you calibrate the tips on your Romer?? That sounds like a classic, tip cal problem - the software thinks the tip is larger than it is. Maybe deflection - I dont really know how the arms "trigger".
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pjleitner over 17 years ago

Tips are calibrated regularly. In fact this occurs even after the arm is calibrated at Romer. They calibrate the tips and the arm all at the same time and send a new "Arm Data" file with the arm.

There is no "trigger" using these hard probes. The probe contacts the part and the operator presses a button to accept the hit.
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Matthew D. Hoedeman over 17 years ago

Tips are calibrated regularly. In fact this occurs even after the arm is calibrated at Romer. They calibrate the tips and the arm all at the same time and send a new "Arm Data" file with the arm.

There is no "trigger" using these hard probes. The probe contacts the part and the operator presses a button to accept the hit.

Then I would bet it is due to the operator pressing too hard while hitting the button. Can't you use a touch-trigger probe in that thing? At least then you would not have operator pressure effecting the results.
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bw_bob over 17 years ago

No help to your problem, but did you try checking the diameters with gage pins & calipers or mics...if your able, just to verify your readings.
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cmmguy over 17 years ago

Good point Bob, measuring Rings would also give the operators instant feed back on their techniques also, sort of a training tool.
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Gregl over 17 years ago

Good point Bob, measuring Rings would also give the operators instant feed back on their techniques also, sort of a training tool.

We almost aways have a ring on our manual CMM for the operators to check the probe calibration with, If I can't get it within .0002 its time for a new tip.
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#2# over 17 years ago

I was told from Romer tech support that it is the deflection of the probe. I find it hard to believe that the probe is deflecting .010 when using the 6mm probe and a soft touch.

Are you saying the diameters are .010 large or small? If that is the case, the probe would only be deflecting .005 (.005 on each side). Could the probe be deflecting that much?
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kass_b over 17 years ago

Make sure your comp is going the right way and have you selected least squares
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